She is also telling friends ... the picture TMZ posted of her smoking from a drug pipe inside her car (below) is not what it seems. She says she was smoking tobacco ... despite the fact that her cup-holders had remnants of what appeared to be marijuana.

As we previously reported, we spoke with several people who have witnessed Amanda's behavior recently, who say she's chatting with inanimate objects ... talking to herself in the gym ... and they fear she may be suffering from serious mental issues.